Non-volatile semiconductor storage device and method of manufacturing the same

ABSTRACT

A non-volatile semiconductor storage device has a plurality of memory strings to each of which a plurality of electrically rewritable memory cells are connected in series. Each of the memory strings includes first semiconductor layers each having a pair of columnar portions extending in a vertical direction with respect to a substrate and a coupling portion formed to couple the lower ends of the pair of columnar portions; a charge storage layer formed to surround the side surfaces of the columnar portions; and first conductive layers formed to surround the side surfaces of the columnar portions and the charge storage layer. The first conductive layers function as gate electrodes of the memory cells.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. §120 from U.S. Ser. No. 13/740,803, filed Jan. 14, 2013,which is a continuation of U.S. Ser. No. 12/679,991, filed Mar. 25,2010, now U.S. Pat. No. 8,372,720, which is a national stage ofPCT/JP2008/072727, filed Dec. 9, 2008, and claims the benefit orpriority under 35 U.S.C. §119 from Japanese Patent Application No. JP2007-320215, filed Dec. 11, 2007, the entire contents of each of whichare incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an electrically rewritable non-volatilesemiconductor storage device and to a method of manufacturing the same.

BACKGROUND ART

Conventionally, LSIs are formed by integrating elements in atwo-dimensional plane on a silicon substrate. Although the size of oneelement is ordinarily reduced (miniaturized) to increase the storagecapacity of a memory, this becomes recently difficult from a viewpointof cost and technology. Although a photolithography technology must beimproved for miniaturization, a cost necessary for a lithography processis more and more increased. Further, even if miniaturization has beenachieved, it is predicted that a withstanding voltage between elementsand the like reaches a physical limit unless a drive voltage and thelike are scaled. That is, there is a high possibility that a devicebecomes difficult to operate.

To cope with the above problem, recently, a lot of semiconductor storagedevices are proposed in which memory cells are three-dimensionallydisposed to increase the degree of integration of the memories (refer toJapanese Patent Application Laid-Open No. 2007-266143 and U.S. Pat. Nos.5,599,724 and 5,707,885).

As one of conventional semiconductor storage devices in which memorycells are disposed three-dimensionally, there is a semiconductor storagedevice using a transistor having a columnar structure (refer to JapanesePatent Application Laid-Open No. 2007-266143 and U.S. Pat. Nos.5,599,724 and 5,707,885). The semiconductor storage device using thetransistor having the columnar structure is provided with amulti-layered conductive layer acting as a gate electrode and apillar-shaped columnar semiconductor. The columnar semiconductorfunctions as a channel (body) of the transistor. A memory gateinsulation layer is disposed around the columnar semiconductor. Anarrangement including the conductive layer, the columnar semiconductorand the memory gate insulation layer is called a memory string.

In the above conventional technology, holes are formed to the laminatedconductive layers at the same time. Subsequently, memory gate insulationlayers are formed to the side walls of the thus formed holes andsubjected to a diluted fluorinated acid process. Then, columnarsemiconductors are formed so that the holes are filled therewith. Thememory cells are three-dimensionally formed by repeating the aboveprocesses a plurality of times. However, a problem arises in that thememory gate insulation layers are removed by etching due to the dilutedfluorinated acid process.

DISCLOSURE OF INVENTION

A non-volatile semiconductor storage device according to one aspect ofthe present invention has a plurality of memory strings in each of whicha plurality of electrically rewritable memory cells are connected inseries, each of the memory strings comprising: first semiconductorlayers each having a pair of columnar portions extending in a verticaldirection with respect to a substrate and a coupling portion formed tocouple the lower ends of the pair of columnar portions; a charge storagelayer formed to surround the side surfaces of the columnar portions; andfirst conductive layers formed to surround the side surfaces of thecolumnar portions and the charge storage layer, the first conductivelayers functioning as gate electrodes of the memory cells.

According to one aspect of the present invention, there is provided amethod of manufacturing a non-volatile semiconductor storage devicehaving a plurality of memory strings in each of which a plurality ofelectrically rewritable memory cells are connected in series, the methodcomprising: forming a first conductive layer on a substrate through afirst insulation layer; forming grooves extending in a first directionthat is in parallel with the substrate so as to dig the first conductivelayers; forming a plurality of second conductive layers on the upperlayers of the first conductive layers through second insulation layers;forming first through holes so that the first through holes pass throughthe second conductive layers and the second insulation layers as well asare aligned with the vicinities of both the ends in the first directionof the grooves; forming charge storage layers to the grooves and sidesurfaces facing the first through holes; and forming first semiconductorlayers to the side surfaces of the charge storage layers.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of an arrangement of a non-volatilesemiconductor storage device 100 according to a first embodiment of thepresent invention;

FIG. 2 is a schematic perspective view of a part of a memory transistorregion 12 according to the first embodiment of the present invention;

FIG. 3 is an enlarged view of one memory string MS according to thefirst embodiment of the present invention;

FIG. 4 is a circuit diagram of the one memory string MS according to thefirst embodiment of the present invention;

FIG. 5 is a sectional view of the memory transistor region 12 accordingto the first embodiment;

FIG. 6 is a sectional view of the memory transistor region 12 accordingto the first embodiment from a terminal end to a peripheral region Ph ina row direction;

FIG. 7 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 8 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 9 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 10 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 11 is a sectional view of the memory transistor region 12 snowing amanufacturing process according to the first embodiment;

FIG. 12 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 13 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 14 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 15 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 16 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 17 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 18 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 19 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 20 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 21 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 22 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 23 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 24 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 25 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 26 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 27 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 28 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 29 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 30 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 31 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 32 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 33 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 34 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 35 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 36 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 37 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 38 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 39 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 40 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 41 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 42 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 43 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 44 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 45 is a sectional view of the memory transistor region 12 showing amanufacturing process according to the first embodiment;

FIG. 46 is a sectional view of the memory transistor region 12 from theterminal end to the peripheral region Ph in the row direction showing amanufacturing process according to the first embodiment;

FIG. 47 is a schematic perspective view of a part of a memory transistorregion of a non-volatile semiconductor storage device according to asecond embodiment of the present invention;

FIG. 48 is a sectional view of the memory transistor region according tothe second embodiment;

FIG. 49 is a schematic perspective view of a part of a memory transistorregion of a non-volatile semiconductor storage device according to athird embodiment of the present invention;

FIG. 50 is a sectional view of the memory transistor region according tothe third embodiment; and

FIG. 51 is a schematic upper surface view of a part of a memorytransistor region of a non-volatile semiconductor storage deviceaccording to a fourth embodiment of the present invention.

EMBODIMENTS

Embodiments of a non-volatile semiconductor storage device and a methodof manufacturing the same according to the present invention will beexplained below referring to the drawings.

First Embodiment Arrangement of Non-Volatile Semiconductor StorageDevice 100 according to First Embodiment

FIG. 1 shows a schematic view of a non-volatile semiconductor storagedevice 100 according to a first embodiment of the present invention. Asshown in FIG. 1, the non-volatile semiconductor storage device 100according to the first embodiment mainly has a memory transistor region12, a word line drive circuit 13, a source side selection gate line(SGS_(m)) drive circuit 14, a drain side selection gate line (SGD_(m))drive circuit 15, a sense amplifier 16, a source line drive circuit 17,and a back gate transistor drive circuit 18. The memory transistorregion 12 has memory transistors for storing data. The word line drivecircuit 13 controls a voltage applied to the word line WL_(m). Thesource side selection gate line (SGS_(m)) drive circuit 14 controls avoltage applied to the source side selection gate line SGS_(m). Thedrain side selection gate line (SGD_(m)) drive circuit 15 controls avoltage applied to the drain side selection gate line (SGD_(m)). Thesense amplifier 16 amplifies an electric potential read out from thememory transistors. The source line drive circuit 17 controls a voltageapplied to a source line SL_(n). The back gate transistor drive circuit18 controls a voltage applied to a back gate line BG. Note that thenon-volatile semiconductor storage device 100 according to the firstembodiment has a bit line drive circuit (not shown) for controlling avoltage applied to a bit line BL_(n) in addition to those describedabove.

FIG. 2 is a schematic perspective view of a part of the memorytransistor region 12 of the non-volatile semiconductor storage device100 according to the first embodiment. In the first embodiment, thememory transistor region 12 has m×n (m, n are natural numbers) pieces ofmemory strings MS each composed of the memory transistors (MTr1 _(mn) toMTr8 _(mn)), a source side select gate transistor SSTr_(mn) and a drainside select gate transistor SDTr_(mn). FIG. 2 shows an example of m=6,n=2. FIG. 3 is a partly enlarged sectional view of FIG. 2.

In the non-volatile semiconductor storage device 100 according to thefirst embodiment, a plurality of the memory strings MS are disposed tothe memory transistor region 12. Although explained below in detail,each of the memory strings MS has such an arrangement that the pluralityof electrically rewritable memory transistors MTr_(mn) are connected inseries. As shown in FIGS. 1 and 2, the memory transistors MTr_(mn)constituting each of the memory strings MS is formed by laminating aplurality of semiconductor layers.

Each memory string MS has a U-shaped semiconductor SC_(mn), word linesWL_(mn) (WL_(m) 1 to WL_(m) 8), the source side selection gate lineSGS_(mn), and the drain side selection gate line SGD_(m). Further, thememory string MS has the back gate line BG.

The U-shaped semiconductor SC_(mn) is formed in a U-shape when viewedfrom a row direction. The U-shaped semiconductor SC_(mn) has a pair ofcolumnar portions CL_(mn) extending in an approximately verticaldirection with respect to a semiconductor substrate Ba and a couplingportion JP_(mn) formed so as to be coupled with lower ends of the pairof columnar portions CL_(mn). Further, as shown in FIG. 3, the U-shapedsemiconductor SC_(mn) has hollow portions H1 which communicate from anupper end of one of the columnar portions CL_(mn) to an upper end of theother columnar portion CL_(mn) through the coupling portion JP_(mn). Aninsulating portion I is formed in the hollow portions H1. Note that thecolumnar portions CL_(mn) may be formed in any of a circular columnarshape and an angular columnar shape. Further, the columnar portionsCL_(mn) may be formed in a stepped columnar shape. Here, the rowdirection is a direction orthogonal to a lamination direction, and acolumn direction to be described later is a direction orthogonal to avertical direction and to the row direction.

The U-shaped semiconductor SC_(mn) is disposed such that a linear lineconnecting the center axes of the pair of columnar portions CL_(mn) isin parallel with the column direction. Further, the U-shapedsemiconductors SC_(mn) are disposed such that they are formed in amatrix state in a plane formed in the row direction and the columndirection.

The word line WL_(mn) of each layer has a shape extending in parallelwith the row direction. The word lines WL_(mn) of the respective layersare repeatedly formed in a line state by being insulated and separatedfrom each other at first intervals formed in the column direction.

Gates of the memory transistors (MTr1 _(mn) to MTr8 _(mn)), which aredisposed at the same positions in the column direction and arranged inthe row direction, are connected to the same word lines WL_(mn). Therespective word lines WL_(mn) are disposed approximately vertical to thememory strings MS. Ends of the word lines WL_(mn) in the row directionare formed stepwise. Note that the ends of the word lines W_(mn) in thecolumn direction are not limited to be formed stepwise. For example, theends of the word lines WL_(mn) in the column direction may be aligned ata certain position in the column direction.

As shown in FIG. 3, an ONO (Oxide-Nitride-Oxide) layer NL is formedbetween the word line WL_(mn) and the columnar portions CL_(mn). The ONOlayer NL has a tunnel insulation layer TI in contact with the columnarportions CL_(mn), a charge storage layer EC in contact with the tunnelinsulation layer TI, and a block insulation layer BI in contact with thecharge storage layer EC. The charge storage layer EC has a function foraccumulating charge.

In other words, the charge storage layer EC is formed so as to surrounda side surface of the columnar portion CL_(mn). Further, each word lineWL_(mn) is formed so as to surround the side surface of the columnarportion CL_(mn) and the charge storage layer EC. Further, each word lineWL_(mn) is divided for each of respective columnar portions CL_(mn)adjacent to each other in the column direction.

The drain side selection gate line SGD_(m) is disposed above theuppermost word line WL_(mn). The drain side selection gate line SGD_(m)has a shape extending in parallel with the row direction. The drain sideselection gate lines SGD_(m) are repeatedly formed in a line state bybeing insulated and separated from each other at first intervals D1 orsecond intervals D2 (D2>D1) formed alternately in the column direction.The drain side selection gate lines SGD_(m) are formed at secondintervals D2 with the source side selection gate line SGS_(m) to bedescribed later sandwiched therebetween. Further, the columnar portionsCL_(mn) are formed passing through the centers of the drain sideselection gate lines SGD_(m) in the column direction. As shown in FIG.3, a gate insulation layer DGI is formed between the drain sideselection gate line SGD_(m) and the columnar portion CL_(mn).

The source side selection gate line SGS_(m) is disposed above theuppermost word line WL_(mn). The source side selection gate line SGS_(m)has a shape extending in parallel with the row direction. The sourceside selection gate lines SGS_(m) are repeatedly formed in a line stateby being insulated and separated from each other at first intervals D1,second intervals D2 formed alternately in the column direction. Thesource side selection gate line SGS_(m) are formed at the secondintervals D2 with the drain side selection gate line SGD_(m) sandwichedtherebetween. Further, the columnar portions CL_(mn) are formed passingthrough the centers of the source side selection gate line SGS_(m) inthe column direction. As shown in FIG. 3, a gate insulation layer SGI isformed between the source side selection gate line SGS_(m) and thecolumnar portion CL_(mn).

In other words, the two drain side selection gate lines SGD_(m) and thetwo source side selection gate lines SGS_(m) are alternately formed byforming the first intervals D1 in the column direction. Further, therespective drain side selection gate lines SGD_(m) and the respectivesource side selection gate lines SGS_(m) are formed to surround thecolumnar portions CL_(mn) and the gate insulation layers SGI, DGI.Further, each drain side selection gate line SGD_(m) and each sourceside selection gate line SGS_(m) are divided for each of respectivecolumnar portions CL_(mn) adjacent to each other in the columndirection.

The back gate line BG is formed to two-dimensionally expand in the rowdirection and the column direction so as to cover below a plurality ofcoupling portions JP_(mn). As shown in FIG. 3, the ONO layer NLdescribed above is formed between the back gate line BG and the couplingportions JP_(mn).

Further, the source lines SL_(n) are formed on upper ends of thecolumnar portions CL_(mn) of the U-shaped semiconductors SC_(mn)adjacent in the column direction.

Further, the bit lines BL_(n) are formed on the upper ends of thecolumnar portions CL_(mn) extending upward of the drain side selectiongate lines SGD_(m) through plug lines PL_(mn). The respective bit linesBL_(n) are formed to be located on the source lines SL_(n). Therespective bit lines BL_(n) are repeatedly formed in a line state whichextends in the column direction at predetermined intervals formed in therow direction.

Next, a circuit arrangement that is arranged by the memory strings MS ofthe first embodiment will be explained referring to FIGS. 2 to 4. FIG. 4is a circuit diagram of one memory string MS of the first embodiment.

As shown in FIGS. 2 to 4, in the first embodiment, each of the memorystrings MS has the eight memory transistors MTr1 _(mn) to MTr8 _(mn),the source side select gate transistor SSTr_(mn), the drain side selectgate transistor SDTr_(mn), and a back gate transistor BGTr_(mn). Theeight memory transistors MTr1 _(mn) to MTr8 _(mn), the source sideselect gate transistor SSTr_(mn), and the drain side select gatetransistor SDTr_(mn) are connected in series, respectively (refer toFIG. 4). Further, a control circuit is connected to the source linesSL_(n).

Each memory transistor MTr_(mn) is composed of the columnar portionsCL_(mn), the ONO layer NL (charge storage layer EC), and the word lineWL_(mn). An end of the word line WL_(mn) in contact with the ONO layerNL functions as a control gate electrode of the memory transistorsMTr_(mn).

The drain side select gate transistor SDTr_(mn) is composed of thecolumnar portions CL_(mn), the gate insulation layer DGI, and the drainside selection gate line SGD_(m). An end of the drain side selectiongate line SGD_(m) in contact with the gate insulation layer DGIfunctions as a control gate electrode of the drain side select gatetransistor SDTr_(mn).

The source side select gate transistor SSTr_(mn) is composed of thecolumnar portions CL_(mn), the gate insulation layer SGI, and the sourceside selection gate line SGS_(m). An end of the source side selectiongate line SGS_(m) in contact with the gate insulation layer SGIfunctions as a control gate electrode of the source side select gatetransistor SSTr_(mn).

The back gate transistor BGTr_(mn) is composed of the coupling portionJP_(mn), the ONO layer NL (charge storage layer EC), and the back gateline BG. An end of the back gate line BG in contact with the ONO layerNL functions as a control gate electrode of the back gate transistorBGTr_(mn).

(Specific Arrangement of Non-Volatile Semiconductor Storage Unit 100according to First Embodiment)

Next, a specific arrangement of the non-volatile semiconductor device100 according to the first embodiment will be explained referring toFIGS. 5 and 6. FIG. 5 is a sectional view of the memory transistorregion 12 of the non-volatile semiconductor device 100 according to thefirst embodiment, and FIG. 6 is a sectional view in the row direction ofa terminal end and a peripheral region Ph of the memory transistorregion 12. Further, FIG. 5 shows a cross section in the column directionand a cross section in the row direction. FIGS. 5 and 6 show a memorystring in which 16 memory transistors are connected in series differentfrom the memory string shown in FIGS. 1 to 4.

First, an arrangement of the memory transistor region 12 of thenon-volatile semiconductor storage device 100 according to the firstembodiment will be explained. As shown in FIGS. 5 and 6, the memorytransistor region 12 (memory string MS) has a back gate transistor layer20, a memory transistor layer 30, a select gate transistor layer 40, anda wiring layer 50 sequentially from the semiconductor substrate Ba inthe lamination direction. The back gate transistor layer 20 functions asthe back gate transistor BGTr_(mn) described above. The memorytransistor layer 30 functions as the memory transistor MTr_(mn)described above. The select gate transistor layer 30 functions as thesource side select gate transistor layer SSTr_(mn) and the drain sideselect gate transistor SDTr_(mn) described above.

The back gate transistor layer 20 has a back gate insulation layers 21and back gate conductive layers 22 sequentially laminated on thesemiconductor substrate Ba. The back gate insulation layers 21 and theback gate conductive layers 22 are formed to expand to an end of thememory transistor region 12 in the row direction and the columndirection. Further, the back gate transistor layer 20 has side wallinsulation layers 23 for covering the side walls of the ends in the rowdirection and the column direction of the back gate insulation layers 21and the back gate conductive layers 22.

The back gate conductive layers 22 are formed to cover the lower surfaceand the side surface of a coupling portion 63 a of a U-shapedsemiconductor layer 63 to be described later and is formed to the sameheight as the upper surface of the coupling portion 63 a.

The back gate insulation layers 21 are composed of silicon oxide (SiO₂).The back gate conductive layers 22 are composed of polysilicon (p-Si).The side wall insulation layers 23 are composed of silicon oxide (SiO₂).

Further, the back gate transistor layer 20 has back gate holes 24 formedby digging the back gate conductive layers 22. Each of the back gateholes 24 has an opening having a short side in the row direction and along side in the column direction. The back gate holes 24 are formed atpredetermined intervals in the row direction and the column direction.In other words, the back gate holes 24 are formed in a plane includingthe row direction and the column direction in a matrix state.

The memory transistor layer 30 has first to fourth inter-word-lineinsulation layers 31 a to 31 d and first to fourth word line conductivelayers 32 a to 32 d alternately laminated on each of the back gateconductive layer 22. Further, the memory transistor layer 30 has a firstseparation/insulation layer 33 a deposited on the fourth the word lineconductive layer 32 d. Further, the memory transistor layer 30 has fifthto eighth inter-word-line insulation layers 31 e to 31 h and fifth toeighth word line conductive layers 32 e to 32 h alternately laminated onthe first separation/insulation layer 33 a. Further, the memorytransistor layer 30 has a second separation/insulation layer 33 b and amemory protection/insulation layer 34 sequentially deposited on theeighth word line conductive layer 32 h.

The first to eighth inter-word-line insulation layers 31 a to 31 h, thefirst to eighth word line conductive layers 32 a to 32 h, the firstseparation/insulation layer 33 a, and the second separation/insulationlayer 33 b are repeatedly formed in a line state so as to extend in therow direction at predetermined intervals formed in the column direction.The first to eighth inter-word-line insulation layers 31 a to 31 h, thefirst to eighth word line conductive layers 32 a to 32 h, the firstseparation/insulation layer 33 a, and the second separation/insulationlayer 33 b are formed stepwise at the ends thereof in the row direction.The memory protection/insulation layer 34 is formed to cover the ends inthe row direction and the column direction of the first to eighthinter-word-line insulation layers 31 a to 31 h, the first to eighth wordline conductive layers 32 a to 32 h, the first separation/insulationlayer 33 a, and the second separation/insulation layer 33 b and theupper surface of the second separation/insulation layer 33 b. Further,silicide films 36 are formed on the side surfaces of the ends in thecolumn direction of the first to eighth word line conductive layers 32 ato 32 h.

The first to eighth inter-word-line insulation layers 31 a to 31 h arecomposed of silicon oxide (SiO₂). The first to eighth word lineconductive layers 32 a to 32 h are composed of polysilicon (p-Si). Thefirst separation/insulation layer 33 a and the secondseparation/insulation layer 33 b are composed of silicon oxide (SiO₂).The memory protection/insulation layer 34 is composed of silicon nitride(SiN). The silicide films 36 are composed of cobalt silicide (CoSi₂).

Further, the memory transistor layer 30 has first memory holes 35 aformed to pass through the first separation/insulation layer 33 a, thefirst to fourth the inter-word-line insulation layers 31 a to 31 d, thefirst to fourth word line conductive layers 32 a to 32 d. The firstmemory holes 35 a are formed to be aligned at positions in the vicinityof both the ends in the column direction of the respective back gateholes 24. Further, the memory transistor layer 30 has second memoryholes 35 b formed to pass through the second separation/insulation layer33 b, the fifth to eighth inter-word-line insulation layers 31 e to 31h, the fifth to eighth word line conductive layers 32 e to 32 h, and thefirst separation/insulation layer 33 a and to dig the fourth word lineconductive layer 32 d. That is, the first memory holes 35 a and thesecond memory holes 35 b are formed such that they are overlapped apredetermined length in the lamination direction. The overlapped lengthis set to an expected maximum amount of offset in alignment, forexample, about one third a minimum feature size. Note that, in FIG. 5,although the center axes of the first memory holes 35 a are offset fromthe center axes of the second memory holes 35 b, these holes 35 a, 35 bmay be formed such that these center axes are aligned with each other.

The select gate transistor layer 40 has drain side conductive layers 41,source side conductive layers 42, and interlayer insulation layers 43which are deposited on the memory protection/insulation layers 34. Thedrain side conductive layers 41, the source side conductive layers 42,the interlayer insulation layers 43 are repeatedly formed in a linestate so as to extend in the row direction at predetermined intervalsformed in the column direction.

The drain side conductive layers 41 are formed by alternately formingfirst intervals D1 or the second intervals D2 in the column direction.Likewise, the source side conductive layers 42 are formed by alternatelyforming first intervals D1 or the second intervals D2 in the columndirection. Two source side conductive layers 41, which are formed at thefirst intervals D1, are formed between the drain side conductive layers41 formed in the column direction at the second intervals D2. Further,two drain side conductive layers 42, which are formed at the firstintervals D1, are formed between the source side conductive layers 42formed in the column direction at the second intervals D2. Theinterlayer insulation layers 43 are formed between the drain sideconductive layers 41 and the source side conductive layers 42 formed asdescribed above.

Further, the select gate transistor layer 40 has select gate transistorinsulation layers 44 formed on the drain side conductive layers 41, thesource side conductive layers 42, and the interlayer insulation layers43.

The drain side conductive layers 41 and the source side conductivelayers 42 are composed of polysilicon (p-Si). The interlayer insulationlayers 43 and the select gate transistor insulation layers 44 arecomposed of silicon oxide (SiO₂).

Further, the select gate transistor layer 40 has drain side holes 45 aformed to pass through the select gate transistor insulation layers 44and the drain side conductive layers 41. Further, the select gatetransistor layer 40 has source side holes 45 b formed to pass throughthe select gate transistor insulation layers 44 and the source sideconductive layers 42. The drain side holes 45 a and the source sideholes 45 b are formed at the positions where they are aligned with thesecond memory holes 35 b. Source line wiring grooves 45 c are formed onthe source side holes 45 b adjacent with each other in the columndirection so as to dig the select gate transistor insulation layers 44.The source line wiring grooves 45 c are formed to connect the upperportions of the source side holes 45 b adjacent to each other in thecolumn direction and to extend in the row direction.

In the above arrangement, drain side gate insulation layers 61 a areformed on side walls facing the drain side holes 45 a. Further, sourceside gate insulation layers 61 b are formed on side walls facing thesource side holes 45 b. Further, memory gate insulation layers 62 areformed to side walls facing the second memory holes 35 b, the firstmemory holes 35 a, and the back gate holes 24. Further, the U-shapedsemiconductor layer 63 is formed up to a first height of the drain sideholes 45 a and the source side holes 45 b so as to come into contactwith the drain side gate insulation layers 61 a, the source side gateinsulation layers 61 b, and the memory gate insulation layers 62. TheU-shaped semiconductor layer 63 has hollow portions. Internal insulationlayers 64 are formed in the hollow portions of the U-shapedsemiconductor layer 63.

The drain side gate insulation layers 61 a and the source side gateinsulation layers 61 b have a cylindrical shape. The memory gateinsulation layers 62 have a U-shape when viewed from the row direction.The memory gate insulation layers 62 have hollow portions which arecontinuous from one upper ends to the other upper ends. The U-shapedsemiconductor layer 63 has a U-shape when viewed from the row direction.The U-shaped semiconductor layer 63 has a pair of columnar portions 63a, which extend in the vertical direction with respect to thesemiconductor substrate Ba when viewed from the row direction, and acoupling portion 63 b formed to couple the lower ends of the pair ofcolumnar portions 63 a.

The U-shaped semiconductor layer 63 functions as the U-shapedsemiconductor SC_(mn) described above. The back gate conductive layer 22functions as the back gate line BG. Further, the ends of the back gateconductive layers 22 in the vicinity of the coupling portions 63 afunction as control gates of the back gate transistors BGTr_(mn). Thefirst to eighth word line conductive layers 32 a to 32 h function as theword lines WL_(m) 1 to WL_(m) 8. Further, the ends of the first toeighth word line conductive layers 32 a to 32 h, which are located inthe vicinity of the columnar portions 63 b, function as control gates ofthe memory transistors MTr_(mn). The drain side conductive layers 41function as the drain side selection gate lines SGD_(m). Further, theends of the drain side conductive layers 41, which are located in thevicinity of the columnar portions 63 b, function as control gates of thedrain side select gate transistors SDTr_(mn). The source side conductivelayers 42 function as the source side selection gate lines SGS_(m).Further, the ends of the source side conductive layers 42, which arelocated in the vicinity of the columnar portions 63 b, function ascontrol gates of the source side select gate transistors SSTr_(mn).Further, the internal dielectric layers 64 correspond to the insulatingportions I.

Further, in the above arrangement, source line conductive layers 65 areformed so that the source line wiring grooves 45 c are filled therewithfrom a first height of the source side holes 45 b. The source lineconductive layers 65 are formed in a sheet shape in parallel with thesemiconductor substrate Ba. The source line conductive layers 65correspond to the source lines SL_(n) described above.

The drain side gate insulation layers 61 a and the source side gateinsulation layers 61 b are composed of silicon oxide (SiO₂). Each of thememory gate insulation layers 62 is composed of the block insulationlayer BI, the charge storage layer EC, and the tunnel insulation layerTI. The block insulation layer BI is composed of silicon oxide (SiO₂).The charge storage layer EC is composed of silicon nitride (SiN). Thetunnel insulation layer TI is composed of silicon oxide (SiO₂). That is,each of the memory gate insulation layers 62 is composed of the ONOlayer. The U-shaped semiconductor layer 63 is composed of polysilicon(p-Si). Each of the internal dielectric layers 64 is composed of siliconoxide (SiO₂). The source line conductive layer 65 is composed oftitanium (Ti), titanium nitride (TiN), and tungsten (W).

The wiring layer 50 has a first wiring insulation layer 51, a secondwiring insulation layer 52, a third wiring insulation layer 53, and afourth wiring insulation layer 54 sequentially laminated on each of theselect gate transistor insulation layers 44.

The first to third wiring insulation layers 51 to 53 are composed ofsilicon oxide (SiO₂). The fourth wiring insulation layer 54 is composedof silicon nitride (SiN).

Further, the wiring layer 50 has bit line wiring grooves 56 a, which areformed to dig the first wiring insulation layer 51, and the bit lineplug holes 56 which are formed to pass through the first wiringinsulation layer 51 from under the bit line wiring grooves 56 a.

The bit line wiring grooves 56 a are formed at the positions where theyare aligned with the bit line plug holes 56. The bit line wiring grooves56 a are repeatedly formed in a line state so as to extend in the columndirection at predetermined intervals formed in the row direction. Thebit line plug holes 56 are formed at the positions where they arealigned with the drain side holes 45 a.

Bit line conductive layers 55 are formed in the bit line wiring grooves56 a. The bit line conductive layers 55 correspond to the bit linesBL_(n) described above. Further, bit line plug layers 57 are formed fromthe upper surface of the U-shaped semiconductor layer 63 in the drainside holes 45 a to the openings of the bit line plug holes 56. The bitline conductive layers 55 are repeatedly formed in a line state so as toextend in the column direction at predetermined intervals formed in therow direction. Further, the bit line plug layers 57 are formed in acolumnar shape so as to come into contact with the lower surfaces of thebit line conductive layers 55.

The bit line conductive layers 55 are composed of tantalum (Ta),tantalum nitride (TaN), copper (Cu). The bit line plug layers 57 arecomposed of titanium (Ti), titanium nitride (TiN), and tungsten (W).

Next, the peripheral region Ph of the non-volatile semiconductor storagedevice according to the first embodiment will be explained. As shown inFIG. 6, in the peripheral region Ph, a base region 71 is formed on thesemiconductor substrate Ba.

Gate insulation layers 81 and gate conductive layers 82 are disposed onthe base region 71 of the semiconductor substrate Ba. Further, side wallinsulation layers 83 are disposed on the side walls of the gateinsulation layers 81 and the gate conductive layers 82. Morespecifically, transistors are composed of the base region 71, the gateinsulation layers 81, and the gate conductive layers 82 in theperipheral region Ph. The transistors are used for a periphery circuitformed in the peripheral region Ph.

Further, the interlayer insulation layers 43 are formed up to the uppersurfaces of the drain side conductive layers 41 and the source sideconductive layers 42 of the memory transistor region 12 so that the gateinsulation layers 81, the gate conductive layers 82, and the side wallinsulation layer 83 are filled therewith. Further, the select gatetransistor insulation layers 44 are formed on the interlayer insulationlayers 43.

Further, in the peripheral region Ph, the first wiring insulation layer51, the second wiring insulation layer 52, third wiring layers 84, thethird wiring insulation layer 53, and the fourth wiring insulation layer54, which are sequentially laminated, are formed on each of the selectgate transistor insulation layers 44.

First plug holes 85 a are formed in the peripheral region Ph so as topass through the select gate transistor insulation layers 44 or theselect gate transistor insulation layers 44 and the interlayerinsulation layers 43. The first plug holes 85 a are formed to reach thedrain side conductive layers 41, the source side conductive layers 42,the first to eighth word line conductive layers 32 a to 32 h, the backgate conductive layers 22, the gate conductive layers 82, and the baseregion 71.

First wiring grooves 85 b, which extend in the column direction so as todig the select gate transistor insulation layers 44, are formed to theupper portions of the first plug holes 85 a. Second plug holes 85 c areformed to the upper portions of the first wiring grooves 85 b at theposition where they are aligned with the first plug holes 85 a so as topass through the first wiring insulation layer 51. Second wiring grooves85 d, which extend in the row direction or in the column direction so asto dig the first wiring insulation layer 51, are formed to the upperportions of the second plug holes 85 c. Third plug holes 85 e are formedto the upper portions of the second wiring grooves 85 d at the positionswhere they are aligned with the second plug holes 85 c so as to passthrough the second wiring insulation layer 52.

First plug conductive layers 86 a are formed in the first plug holes 85a. First wiring layers 86 b are formed in the first wiring grooves 85 b.Second plug conductive layers 86 c are formed in the second plug holes85 c. Second wiring layers 86 d are formed in the second wiring grooves85 d. The third wiring layers 84 are formed in the third plug holes 85 eso as to project downward and come into contact with the upper surfaceof the second wiring layers 86 d.

The first plug conductive layers 86 a, the first wiring layers 86 b, andthe second plug conductive layers 86 c are composed of titanium (Ti),titanium nitride (TiN), and tungsten (W). The second wiring layers 86 dare composed of tantalum (Ta), tantalum nitride (TaN), and copper (Cu).The third wiring layers 84 are composed of titanium (Ti), titaniumnitride (TiN), and aluminum-copper (AlCu).

(Operation of Non-Volatile Semiconductor Storage Device 100 according toFirst Embodiment)

Next, an operation of the non-volatile semiconductor device 100according to the first embodiment will be explained referring to FIGS. 1to 4 again. A “read-out operation”, a “write operation”, and an “eraseoperation” in the memory transistors MTr1 _(mn) to MTr8 _(mn) will beexplained. Note that the “read-out operation” and the “write operation”will be explained as to an example in which the memory transistor MTr4_(mn) is used as a subject from which and to which data is read out andwritten. Further, the explanation will be made assuming that thethreshold value Vth (neutral threshold value) of the transistor MTr,which is in a state that no charge is accumulated in the charge storagelayer EC, is about 0 V.

(Read-Out Operation)

When data is read out from the memory transistor MTr4 _(mn), the bitline drive circuit applies a bit line voltage Vbl to the bit lineBL_(n). The source line drive circuit 17 sets the source line SL_(n) to0 V. The source side selection gate line drive circuit 14 applies adrive voltage Vdd to the source side selection gate line SGS_(m). Thedrain side selection gate line drive circuit 15 applies the drivevoltage Vdd to the drain side selection gate line SGD_(m). The back gateline drive circuit 19 applies a conductive voltage Vj to the back gateline BG. More specifically, the source side select gate transistorSSTr_(mn), the drain side select gate transistor SSTr_(mn), and the backgate transistor BGTr_(mn) are turned ON.

Further, when data is read out, the word line drive circuit 13 sets theword line WL_(m) 4, to which a bit (MTr4 _(mn)) from which data isdesired to be read out is connected, to 0 V. In contrast, the word linedrive circuit 13 sets the word lines WL_(mn), to which the other bitsare connected, to a read-out voltage Vread (for example, 4.5 V). Withthis operation, whether or not a current flows to the bit line BL_(n) isdetermined depending on whether or not the threshold value voltage Vthof the memory transistor MTr4 _(mn) from which the data is desired to beread out is set equal to or larger or smaller than 0 V. Therefore, thedata information of the memory transistor MTr4 _(mn) can be read out bysensing the current of the bit line BL_(n) by the sense amplifier 16.

(Write Operation)

When data “0” is written to the memory transistor MTr4 _(mn), that is,when electrons are injected into the charge storage layer EC of thememory transistor MTr4 _(mn) and the threshold value voltage Vth of thememory transistor MTr4 _(mn) is increased, the bit line drive circuitsets the bit line BLm to 0 V. The source line drive circuit 17 appliesthe drive voltage Vdd (for example, 3 V) to the source line SL_(n). Thesource side selection gate line drive circuit 14 applies an off voltageVoff (for example, 0 V) to the source side selection gate line SGS_(m).The drain side selection gate line drive circuit 15 applies the drivevoltage Vdd to the drain side selection gate line SGD_(m). The back gateline drive circuit 19 applies the conductive voltage Vj to the back gateline BG.

Further, when the data “0” is written, the word line drive circuit 13applies a program voltage Vprog (for example, 18 V) to the word lineWL_(m) 4 of the bit (MTr4 _(mn)) to which the data is desired to bewritten. In contrast, the word line drive circuit 13 applies a passvoltage Vpass (for example, 10 V) to the other word lines WL_(mn). Withthis operation, since the electric field strength that is applied to thecharge storage layer EC of only in the desired bit (MTr4 _(mn)) isincreased and the electrons are injected into the charge storage layerEC, the threshold value voltage Vth of the memory transistor MTr4 _(mn)shifts in a positive direction.

When data “1” is written to the memory transistor MTr4 _(mn), that is,when the threshold value voltage Vth of the memory transistor MTr4 _(m)is not increased from an erase state (when no electrons are injectedinto the charge storage layer EC), the bit line drive circuit appliesthe drive voltage Vdd to the bit line BL_(n). Note that the other drivecircuits execute the same operation as that when the data “0” iswritten. Application of the drive voltage Vdd to the bit line BL_(n)makes the gate electric potential of the drain side select gatetransistor SDTr_(mn) the same as the source electric potential thereof.With this operation, since the drain side select gate transistorSDTr_(mn) is turned OFF and the electric potential difference betweenthe channel forming region (body portion) of the memory transistor MTr4_(mn) and the word line WL_(m) 4 is reduced, electrons are not injectedinto the charge storage layer EC of the memory transistor MTr4 _(mn).

(Erase Operation)

When data is erased, the data of the memory transistors is erased in ablock unit composed of a plurality of memory strings MS.

First, the back gate line drive circuit 19 applies the conductivevoltage Vj to the back gate line BG. Subsequently, in a selected block(block from which data is desired to be erased), an erase voltage Verase(for example, 20 V) is applied to one end of the source line SL_(n) andfurther the source line SL_(n) is placed in a floating state. Then, thesource side selection gate line drive circuit 14 increases the electricpotential of the source side select gate transistor SSTr_(mn) (forexample, 15 V) at a timing somewhat offset from the timing at which thesource line SL_(n) is placed in the floating state. Likewise, the drainside selection gate line drive circuit 15 increases the electricpotential of the drain side select gate transistor SDTr_(mn) (forexample, 15 V). With these operations, a GIDL (Gate Induced Drain Leak)current is generated in the vicinity of a gate end of the source sideselect gate transistor SSTr_(mn), and created holes flow into thecolumnar portions CL_(mn) acting as body portions of the memorytransistors MTr1 _(mn) to MTr8 _(mn). In contrast, electrons flow in thedirection of the source line SL_(n). With these operations, since anelectric potential, which is near to the erase voltage Verase, istransmitted to the channel forming region (body portion) of the memorytransistor MTr, when the word drive circuit 13 sets the word linesWL_(m) 1 to WL_(m) 8 to, for example, 0 V, the electrons of the chargestorage layer EC of the memory transistors MTr1 _(mn) to MTr8 _(mn) areextracted. That is, the data of the memory transistors MTr1 _(mn) toMTr8 _(mn) is erased.

In contrast, when the data of the memory transistors of the selectedblock is erased, the word lines WL_(m) 1 to WL_(m) 8 are placed in thefloating state in the non-selected blocks. With this operation, anincrease of the electric potential of the channel forming regions (bodyportions) of the memory transistors MTr1 _(mn) to MTr8 _(mn) increasesthe electric potential of the word lines WL_(m) 1 to WL_(m) 8 bycoupling. Accordingly, since an electric potential difference is notcaused between the word lines WL_(m) 1 to WL_(m) 8 and the chargestorage layers EC of the memory transistors MTr 1 to MTr8 _(mn),electrons are not extracted (erased) from the charge storage layers EC.

(Method of Manufacturing Non-Volatile Semiconductor Storage Device 100According to First Embodiment)

Next, a method of manufacturing the non-volatile semiconductor storagedevice 100 according to the first embodiment will be explained referringto FIGS. 7 to 46. The drawings denoted by the odd figure numbers inFIGS. 7 to 45 are sectional views showing the memory transistor region12. The drawings denoted by the odd figure numbers in FIGS. 7 to 45 aresectional views in the row direction and sectional views in the columndirection. The drawings denoted by the even numbers in FIGS. 8 to 45 aresectional views in the column direction showing a terminal end and aperipheral region Ph of the memory transistor region 12.

First, as shown in FIGS. 7 and 8, the semiconductor substrate Ba inwhich the base region 71 is formed on the front surface of a positionacting as the peripheral region Ph, is prepared. Next, after siliconoxide (SiO₂) and polysilicon (p-Si) are deposited on the semiconductorsubstrate Ba, the back gate insulation layer 21, the back gateconductive layer 22, and the side wall insulation layer 23 are formed inthe memory transistor region 12 using a lithography method, a RIE(Reactive Ion Etching) method, and an ion implantation method. Further,the gate insulation layer 81, the gate conductive layer 82, and the sidewall insulation layer 83 are formed in the peripheral region Ph.

Next, as shown in FIGS. 9 and 10, in the peripheral region Ph, siliconoxide (SiO₂) is deposited from the upper surface of the semiconductorsubstrate Ba to the upper surface of the gate conductive layer 82 (backgate conductive layer 22), and the interlayer insulation layer 83 a isformed. Subsequently, the back gate holes 24 are formed in the memorytransistor region 12 by etching the back gate conductive layer 22. Eachof the back gate holes 24 is formed to have an island-shaped openinghaving a long side in the column direction and a short side in the rowdirection. The back gate holes 24 are formed at predetermined intervalsin the row direction and the column direction. Next, silicon nitride(SiN) is deposited so that the back gate holes 24 are filled therewith.Subsequently, the silicon nitride (SiN) of the upper portion of the backgate conductive layer 22 is removed using a chemical mechanicalpolishing (CMP) method or a RIE method, and first sacrificial layers 91are formed in the back gate holes 24. Note that although the back gateholes 24 are formed up to such a depth that they do not pass through theback gate conductive layer 22 as shown in FIG. 9, they may be formed topass through the back gate conductive layer 22.

Next, as shown in FIGS. 11 and 12, silicon oxide (SiO₂) and polysilicon(p-Si) are alternately laminated on the back gate conductive layer 22,the sacrificial layers 91, the gate conductive layer 82, and theinterlayer insulation layer 83 a, and first to fourth sheet-shapedinter-word-line insulation layers 31 a′ to 31 d′, first to fourthsheet-shaped polysilicon conductive layers 32 a′ to 32 d′, and a firstsheet-shaped separation/insulation layer 33 a′ are formed. The first tofourth sheet-shaped inter-word-line insulation layers 31 a′ to 31 d′,the first to fourth sheet-shaped polysilicon conductive layers 32 a′ to32 d′, and the first sheet-shaped separation/insulation layer 33 a′ areformed to two-dimensionally expand in directions orthogonal to thelamination direction (row direction and column direction).

Subsequently, the first memory holes 35 a are formed to pass through thefirst to fourth sheet-shaped inter-word-line insulation layers 31 a′ to31 d′, the first to fourth sheet-shaped polysilicon layers 32 a′ to 32d′, and the first sheet-shaped separation/insulation layer 33 a′.Further, the first memory holes 35 a are formed at the positions wherethey are aligned with the vicinities of both the ends in the columndirection of the back gate holes 24. Silicon nitride (SiN) is depositedin the first memory holes 35 a, and second sacrificial layers 92 a areformed.

Subsequently, silicon oxide (SiO₂) and polysilicon (p-Si) arealternately laminated on the first sheet-shaped separation/insulationlayer 33′a, and fifth to eighth sheet-shaped inter-word-line insulationlayers 31 e′ to 31 h′, fifth to eighth sheet-shaped polysilicon layers32 e′ to 32 h′, and second sheet-shaped separation/insulation layer 33b′ are formed. The fifth to eighth sheet-shaped inter-word-lineinsulation layers 31 e′ to 31 h′, the fifth to eighth sheet-shapedpolysilicon layers 32 e′ to 32 h′, and the second sheet-shapedseparation/insulation layer 33 b′ are formed to two-dimensionally expandin directions orthogonal to the lamination direction (row direction andcolumn direction).

Subsequently, the second memory holes 35 b are formed such that theypass through the second sheet-shaped separation/insulation layer 33 b′,the fifth to eighth sheet-shaped inter-word-line insulation layers 31 e′to 31 h′, the fifth to eighth sheet-shaped polysilicon layers 32 e′ to32 h′, and the first sheet-shaped separation/insulation layer 33 a′ andetch the fourth sheet-shaped word line polysilicon layer 32 d′. Further,the second memory holes 35 b are formed at the positions where they arealigned with the first memory holes 35 a. Silicon nitride (SiN) isdeposited in the second memory holes 35 b, and the third sacrificiallayers 92 b are formed.

Next, as shown in FIGS. 13 and 14, the first sacrificial layers 91, thesecond sacrificial layers 92 a, and the third sacrificial layers 92 bare removed. Inc first sacrificial layers 91, the second sacrificiallayers 92 a, and the third sacrificial layer 92 b are removed in, forexample, a heated phosphoric acid solution. The first memory holes 35 a,the second memory holes 35 b, and the back gate holes 24 are formedagain through the processes shown in FIGS. 13 and 14. The first memoryholes 35 a, the second memory holes 35 b, and the back gate holes 24communicate with each other and are formed in a U-shape when viewed fromthe row direction. Subsequently, the front surface of the exposed backgate conductive layer 22 and the front surfaces of exposed first toeighth sheet-shaped polysilicon layer 32 a′ to 32 h′ are rinsed by adiluted fluorinated acid process to thereby remove natural oxide films.

Subsequently, as shown in FIGS. 15 and 16, the memory gate insulationlayers 62 are formed so as to cover the side walls, which face the backgate holes 24, the first memory holes 35 a, and the second memory holes35 b, and to cover the second sheet-shaped separation/insulation layer33 b′. Specifically, silicon oxide (SiO₂), silicon nitride (SiN), andsilicon oxide (SiO₂) are deposited, and the memory gate insulationlayers 62 are formed.

Next, as shown in FIGS. 17 and 18, amorphous silicon (a-Si) is depositedon the memory gate insulation layers 62, and an amorphous silicon layer93 is formed. The amorphous silicon layer 93 is formed to have hollowportions 93 a. In other words, the amorphous silicon layer 93 is formedso that the back gate holes 24, the first memory holes 35 a, and thesecond memory holes 35 b are not completely filled therewith.

Subsequently, as shown in FIGS. 19 and 20, the side walls of theamorphous silicon layer 93 facing the hollow portions 93 a are thermallyoxidized, and silicon oxide (SiO₂) is formed. Further, the remainingamorphous silicon layer 93 is crystallized, polysilicon (p-Si) isformed, and the U-shaped semiconductor layer 63 is formed. Silicon oxide(SiO₂) is further deposited on the silicon oxide (SiO₂) formed in thehollow portions 93 a of the U-shaped semiconductor layer 63 a using aCVD (Chemical Vapor Deposition) method, and the internal dielectriclayers 64 are formed so that hollow portions 93 a are filled therewith.Further, the memory gate insulation layers 62, the U-shapedsemiconductor layer 63, and the internal dielectric layers 64 depositedon the second sheet-shaped separation/insulation layer 33B′ are removedby a CMP process.

Next, as shown in FIGS. 21 and 22, the ends of the first to eighthsheet-shaped inter-word-line insulation layers 31 a′ to 31 h′, the firstto eighth sheet-shaped polysilicon layers 32 a′ to 32 h′, and the firstand second sheet-shaped separation/insulation layers 32 a′, 32 b′ on theperipheral region Ph side are processed stepwise. This process isexecuted by repeating, for example, slimming and RIE (or lithography) ofa resist film.

Subsequently, as shown in FIGS. 23 and 24, silicon nitride (SiN) isdeposited to cover the second sheet-shaped separation/insulation layer33 b′ and the ends processed stepwise in the memory transistor region12, and the memory protection/insulation layers 34 are formed. Next,silicon oxide (SiO₂) is deposited up to the uppermost surface of thememory protection/insulation layers 34 in the memory transistor region12 and the peripheral region Ph, and the interlayer insulation layers 43are formed.

Next, as shown in FIGS. 25 and 26, memory separation grooves 94 arerepeatedly formed in a line state so as to extend in the row directionat predetermined intervals formed in the column direction in the memorytransistor region 12. The memory separation grooves 94 are formed toposition between the first memory holes 35 a and the second memory holes35 b in the column direction. The memory separation grooves 94 areformed to pass through the memory protection/insulation layers 34′, thefirst to eighth sheet-shaped inter-word-line insulation layers 31 a′ to31 h′, the first to eighth sheet-shaped polysilicon layers 32 a′ to 32h′, and the first and second separation/insulation layers 33 a′, 33 b′.

The first to eighth sheet-shaped inter-word-line insulation layers 31 a′to 31 h′ are made to the first to eighth inter-word-line insulationlayers 31 a to 31 h, which have a shape extending in parallel with eachother in the row direction and are repeatedly formed in the line-stateat the first intervals formed in the column direction by the processesof forming the memory separation grooves 94 shown in FIGS. 25 and 26.Further, the first to eighth sheet-shaped polysilicon layers 32 a′ to 32h′ are made to the first to eighth word line conductive layers 32 a to32 h which have a shape extending in parallel with each other in the rowdirection and repeatedly formed in the line-state at the first intervalsformed in the column direction. Further, the first and secondsheet-shaped separation/insulation layer 33 a′ and 33 b′ are made to thefirst and second separation/insulation layer 33 a and 33 b which have ashape extending in parallel with each other in the row direction andrepeatedly formed in the line-state at the first intervals formed in thecolumn direction.

Subsequently, as shown in FIGS. 27 and 28, cobalt (Co) films aredeposited on the side surfaces of the memory separation grooves 94 byCVD. Thereafter, a RTA (Rapid Thermal Annealing) process is furtherexecuted so that cobalt films react with polysilicon (p-Si) thatconstitutes the first to eighth word line conductive layers 32 a to 32 hin a self-alignment manner, and the silicide films 36 are formed on thefront surfaces of the first to eighth word line conductive layers 32 ato 32 h. Note that unreacted cobalt films are removed in a sulfuricacid-hydrogen peroxide water mixed solution.

Next, as shown in FIGS. 29 and 30, the memory separation grooves 94 arefilled with silicon nitride (SiN) so that the memoryprotection/insulation layers 34 are formed to extend into the memoryseparation grooves 94.

Subsequently, polysilicon (p-Si) is deposited on the memoryprotection/insulation layers 34. Then, select gate transistor separationgrooves 95 are formed at the positions where they are aligned with thememory separation grooves 94. The select gate transistor separationgrooves 95 are repeatedly formed in a line state at predeterminedintervals formed in the column direction. The drain side conductivelayers 41 and the source side conductive layers 42 are formed by theabove processes.

Next, as shown in FIGS. 31 and 32, silicon oxide (SiO₂) is deposited onthe drain side conductive layers 41 and the source side conductivelayers 42, and the select gate transistor insulation layers 44 areformed. Subsequently, the drain side holes 45 a are formed to passthrough the select gate transistor insulation layers 44, the drain sideconductive layers 41, and the memory protection/insulation layers 34 sothat they are aligned with the second memory holes 35 b. Further, thesource side holes 45 b are formed to pass through the select gatetransistor insulation layers 44, the source side conductive layers 42,and the memory protection/insulation layers 34 so that they are alignedwith the second memory holes 35 b.

Next, as shown in FIGS. 33 and 34, after silicon nitride (SiN) isdeposited, a lithography process is executed. The drain side gateinsulation layers 61 a and the source side gate insulation layers 61 bare formed to the side walls of the drain side holes 45 a and the sourceside holes 45 b by the process.

Subsequently, polysilicon (p-Si) is deposited up to a predeterminedposition higher than the drain side conductive layers 41 and the sourceside conductive layers 42 so that it comes into contact with the gateinsulation layers 61 a in the drain side holes 45 a and the source sideholes 45 b. That is, the U-shaped semiconductor layer 63 is formed sothat the upper surface thereof extends to a predetermined positionhigher than the drain side conductive layers 41 and the source sideconductive layers 42.

Next, as shown in FIGS. 35 and 36, the first plug holes 85 a are formedto pass through the select gate transistor insulation layers 44, theinterlayer insulation layers 43, and the memory protection/insulationlayers 34 in the peripheral region Ph. The first plug holes 85 a areformed to reach the base region 71, the gate conductive layers 82, theback gate conductive layer 22, the first to eighth word line conductivelayer 32 a to 32 h, the drain side conductive layers 41, and the sourceside conductive layers 42. Note that, in FIG. 36, illustration of thefirst plug holes 85 a, which reach the source side conductive layer 42,and illustration of the first plug holes 85 a, which reach the firstword line conductive layer 32 a and the third to eighth the word lineconductive layers 32 c to 32 h, are omitted.

Subsequently, as shown in FIGS. 37 and 38, the select gate transistorinsulation layers 44 are dug so that the upper portions of the sourceside holes 45 b adjacent to each other in the column direction areconnected in the column direction, and the source line wiring grooves 45c are formed. The source line wiring grooves 45 c are formed to haverectangular openings each having a long side in the row direction and ashort side in the column direction. At the same time, the select gatetransistor insulation layers 44 are etched in the upper portions of thefirst plug holes 85 a, and the first wiring grooves 85 b are formed inthe peripheral region Ph.

Next, as shown in FIGS. 39 and 40, titanium (Ti), titanium nitride(TiN), and tungsten (W) are sequentially deposited so that the sourceline wiring grooves 45 c, the first wiring grooves 85 b, and the firstplug holes 85 a are filled therewith. Thereafter, the titanium (Ti), thetitanium nitride (TiN), and the tungsten (W) deposited on the uppersurfaces of the select gate transistor insulation layers 44 are removedby CMP. The source line conductive layer 65 is formed so as to fill thesource line wiring grooves 45 c through the above process (so-called,dual damascene process). Further, the first plug conductive layers 86 aare formed so that the first plug holes 85 a are filled therewith, andthe first wiring layers 86 b are formed so that the first wiring grooves85 b are filled therewith.

Subsequently, as shown in FIGS. 41 and 42, silicon oxide (SiO₂) isdeposited on the select gate transistor insulation layers 44, and thefirst wiring insulation layer 51 is formed. Next, the bit line plugholes 56 and the second plug holes 85 c are formed to pass through thefirst wiring insulation layer 51. The bit line plug holes 56 are formedat the positions where they are aligned with the drain side holes 45 a.Further, the second plug holes 85 c are formed at the positions wherethey are aligned with the first memory holes 85 a.

Next, titanium (Ti), titanium nitride (TiN), and tungsten (W) aresequentially deposited so that the bit line plug holes 56 and the secondplug holes 85 c are filled therewith. Subsequently, the titanium (Ti),the titanium nitride (TiN), and the tungsten (W) on the first wiringinsulation layer 51 are removed by CMP. The bit line plug layers 57 areformed in the bit line plug holes 56 through the processes shown inFIGS. 41 and 42. Further, the second plug conductive layers 86 c areformed in the second plug holes 85 c.

Subsequently, as shown in FIGS. 43 and 44, silicon oxide (SiO₂) isdeposited so that the upper surface of the first wiring insulation layer51 is made much higher. Next, the bit line wiring grooves 56 a areformed by etching he first wiring insulation layer 51.

The bit line wiring grooves 56 a are formed at the positions where theyare aligned with the bit line plug holes 56. The bit line wiring grooves56 a are repeatedly formed in the line state so as to extend in thecolumn direction at the predetermined intervals formed in the rowdirection. Further, the second wiring grooves 85 d are formed by etchingthe first wiring insulation layer 51 in the peripheral region Ph.

Next, tantalum (Ta), tantalum nitride (TaN), and copper (Cu) aresequentially deposited so that the bit line wiring grooves 56 a and thesecond wiring grooves 85 d are filled therewith. Subsequently, thetantalum (Ta), the tantalum nitride (TaN), and the copper (Cu) on thefirst wiring insulation layer 51 are removed by CMP. The bit lineconductive layers 55 are formed to the bit line wiring grooves 56 athrough the above processes. Further, the second wiring layers 86 d areformed to the second wiring grooves 85 d.

Subsequently, as shown in FIGS. 45 and 46, silicon oxide (SiO₂) isdeposited on the first wiring insulation layer 51, and the second wiringinsulation layer 52 is formed. The third plug holes 85 e are formed topass through the second wiring insulation layer 52 in the peripheralregion Ph. The third plug holes 85 e are formed at the positions wherethey are aligned with the second wirings grooves 85 d. Subsequently,titanium (Ti), titanium nitride (TiN), and aluminum-copper (AlCu) aresequentially deposited to a predetermined height on the upper surface ofthe second wiring insulation layer 52 so that the third plug holes 85 eare filled therewith. Next, the titanium (Ti), the titanium nitride(TiN), and the aluminum-copper (AlCu) are processed to a predeterminedshape. The third wiring layers 84 are formed from the titanium (Ti)—thetitanium nitride (TiN)—the aluminum-copper (AiCu) through the aboveprocesses. Further, bonding pads (not shown) are formed through the sameprocesses.

Subsequent to FIGS. 45 and 46, silicon oxide (SiO₂) and silicon nitride(SiN) are deposited on the second wiring insulation layer 52 and thethird wiring layers 84, and the third wiring insulation layer 53 and thefourth wiring insulation layer 54 are formed. The non-volatilesemiconductor storage device 100 according to the first embodiment shownFIGS. 5 and 6 is manufactured through the above processes.

(Advantage of Non-Volatile Semiconductor Storage Device 100 according toFirst Embodiment)

Next, an advantage of the non-volatile semiconductor storage deviceaccording to the first embodiment will be explained. The non-volatilesemiconductor storage device 100 according to the first embodiment canbe highly integrated as shown in the above laminated structure. Further,as explained in the above manufacturing processes, in the non-volatilesemiconductor storage device 100, the respective layers acting as thememory transistors MTr_(mn) and the respective layers acting as thesource side select gate transistor SSTr_(mn) and the drain side selectgate transistor layers SDTr_(mn) can be manufactured by thepredetermined number of lithography processes regardless of laminatednumber of the word lines WL_(mn). That is, the non-volatilesemiconductor storage device 100 can be manufactured at a less expensivecost.

Further, the non-volatile semiconductor storage device 100 according tothe first embodiment has the back gate line BG which is in contact withthe coupling portion JP_(mn) (U-shaped lower portion) of the U-shapedsemiconductor layer SC_(mn). Then, the back gate line BG functions asthe back gate transistor BGTr_(mn) for forming a channel to the couplingportion JP_(mn). Accordingly, the memory strings MS having excellentconductivity can be arranged by the U-shaped semiconductor layer SC_(mn)in an almost non-doped state.

Further, in the non-volatile semiconductor storage device 100 accordingto the first embodiment, the source line SL_(n) (source line conductivelayer 65) is composed of titanium (Ti), titanium nitride (TiN), andtungsten (W). Accordingly, the non-volatile semiconductor storage device100 according to the first embodiment can improve a read-out speed ascompared with a case that the source line SL_(n) is composed of asemiconductor of polysilicon and the like.

A comparative example, in which a U-shaped semiconductor layer 63 isformed by depositing polysilicon a plurality of times, will becontemplated here. In the manufacturing process of the comparativeexample, polysilicon is formed in, for example, first memory holes 35 ain place of the sacrificial layers 91. Subsequently, fifth to eighthword line conductive layers 32 e to 32 h are formed on the polysilicon,second memory holes 35 b are formed, and memory gate insulation layers32 are formed in the second memory holes 35 b.

In the comparative example, when the polysilicon is deposited in thesecond memory holes 35 b subsequently, it is necessary to remove naturaloxide films on the bottoms of the second memory holes 35 b (uppersurface of the polysilicon in the first memory holes 35 a) by a wetprocess. However, a problem arises in that the memory gate insulationlayers 32 in the second memory holes 35 b are removed by etching due tothe wet process.

Further, in the manufacturing process of the comparative example, acontact resistance is generated between the polysilicon in the firstmemory holes 35 a and the polysilicon in the second memory holes 35 b.The contact resistance makes a current flowing in the U-shapedsemiconductor layer 63 unstable.

In contrast, in the manufacturing process of the non-volatilesemiconductor storage device 100 according to the first embodiment, thememory gate insulation layers 62 and the U-shaped semiconductor layer 63can be formed without executing the wet process. More specifically, thememory gate insulation layers 62 and the U-shaped semiconductor layer 63are continuously formed in the back gate holes 24, the first memoryholes 35 a, and the second memory holes 35 b. Accordingly, in thenon-volatile semiconductor storage device 100 according to the firstembodiment, the memory gate insulation layers 62 can be formed in apredetermined thickness without being removed by etching. Further, sincethe wet process is not necessary, a material that constitutes the memorygate insulation layers 62 can be selected from a wide range.Accordingly, the memory gate insulation layers 62 can be composed of amaterial corresponding to multi-valuation. As a result, the density of amemory device can be more increased.

Further, since the U-shaped semiconductor layer 63 is continuouslyformed, no contact resistance is generated in the boundary between thefirst memory holes 35 a and the second memory holes 35 b. Thus, in thenon-volatile semiconductor storage device 100 according to the firstembodiment, the U-shaped semiconductor layer 63 can cause a current toflow more stably than the comparative example.

Further, in the non-volatile semiconductor storage device 100 accordingto the first embodiment, the U-shaped semiconductor layer 63 is formedto have the hollow portions. With this arrangement, the U-shapedsemiconductor layer 63 having a predetermined thickness can be formedwithout depending on the diameter of the back gate holes 24, thediameter of the first memory holes 35 a, and the diameter of the secondmemory holes 35 b. More specifically, in the non-volatile semiconductordevice 100 according to the first embodiment, the characteristics of thememory transistors MTr_(mn) can be kept regardless of the dispersion ofthe diameters of openings in manufacture.

Further, in the non-volatile semiconductor storage device 100 accordingto the first embodiment, the first memory holes 35 a and the secondmemory holes 35 b are formed by being overlapped in the laminationdirection. Accordingly, even if the center positions of the first memoryholes 35 a are offset from the center positions of the second memoryholes 35 b a predetermined length, the first memory holes 35 a can becaused to communicate with the second memory holes 35 b. Morespecifically, the reliability of the non-volatile semiconductor storagedevice 100 according to the first embodiment can be enhanced as well asthe decrease of yield thereof can be suppressed.

Further, in the non-volatile semiconductor device 100 according to thefirst embodiment, the drain side select gate transistor layer 41 and thesource side select gate transistor layer 42 are composed of the samedeposited layer. Accordingly, the process cost of the non-volatilesemiconductor device 100 according to the first embodiment can bereduced.

As described above, the non-volatile semiconductor storage device 100according to the first embodiment has high reliability and can bemanufactured less expensively.

Second Embodiment Arrangement of Non-Volatile Semiconductor StorageDevice According to Second Embodiment

Next, an arrangement of a non-volatile semiconductor storage deviceaccording to a second embodiment will be explained referring to FIGS. 47and 48. FIG. 47 is a schematic perspective view of a part of a memorytransistor region of the non-volatile semiconductor storage deviceaccording to the second embodiment, and FIG. 48 is a sectional view ofthe memory transistor region.

As shown in FIGS. 47 and 48, a memory transistor layer 30 a and a selectgate transistor layer 40 a in the non-volatile semiconductor storagedevice according to the second embodiment are arranged different fromthose of the first embodiment.

In the memory transistor layer 30 a and the select gate transistor layer40 a, a source side selection gate line SGS_(m)′ (source side conductivelayer 421) and word lines WL_(m) 1′ to WL_(m) 8′ (first to eighth wordline conductive layers 321 a to 321 h) are arranged different from thoseof the first embodiment.

Here, a U-shaped semiconductor layer 63 (U-shaped semiconductor layerSC_(mn)) disposed at a predetermined position is shown as a “U-shapedsemiconductor layer 63 (1) (U-shaped semiconductor layer SC_(mn))”.Further, a U-shaped semiconductor layer 63 (U-shaped semiconductor layerSC_(mn)), which is disposed adjacent to a column with respect to the“U-shaped semiconductor layer 63 (1) (U-shaped semiconductor layerSC_(mn)(1))”, is shown as a “U-shaped semiconductor layer 63 (2)(U-shaped semiconductor layer SC_(mn)(2))”.

In the second embodiment, the U-shaped semiconductor layers SC_(mn)(1)and SC_(mn)(2) arranged in a column direction are formed such that theyshare the word lines WL_(m) 1′ to WL_(m) 8′ and the source sideselection gate line SGS_(m)′ in columnar portions CL_(mn). In otherwords, the word lines WL_(m) 1′ to WL_(m) 8′ and the source sideselection gate line SGS_(m)′ are divided by respective pairs of columnarportions CL_(mn) which constitutes U-shaped semiconductor layers SC_(mn)adjacent to each other in the column direction. Note that a drain sideselection gate line SGD_(m) is arranged similar to the first embodiment.A source side selection gate line SGS_(m)′ may be also arranged similarto the first embodiment.

(Method of Manufacturing Non-Volatile Semiconductor Storage DeviceAccording to Second Embodiment)

Next, a method of manufacturing the non-volatile semiconductor storagedevice according to the second embodiment will be explained. In themanufacturing process of the non-volatile semiconductor storage deviceaccording to the second embodiment, memory separation grooves 94 are notformed between the respective U-shaped semiconductor layers 63 adjacentto each other in the column direction in the processes shown in FIGS. 25and 26 of the first embodiment. In other words, in the manufacturingprocess of the non-volatile semiconductor storage device according tothe second embodiment, the memory separation grooves 94 are formed onlyat the centers in the column direction of the respective U-shapedsemiconductor layers 63. Thereafter, the non-volatile semiconductorstorage device according to the second embodiment is manufacturedthrough the same processes as the first embodiment.

(Advantage of Non-Volatile Semiconductor Storage Device According toSecond Embodiment)

The non-volatile semiconductor storage device according to the secondembodiment achieves the same advantage as the first embodiment.

Further, in the non-volatile semiconductor storage device according tothe second embodiment, the word lines WL_(m) 5′ to WL_(m) 8′ and thesource side selection gate line SGS_(m)′ are formed to surround a pairof the columnar portions CL_(mn) adjacent to each other in the columndirection. That is, the word lines WL_(m) 1′ to WL_(m) 8′ and the sourceside selection gate line SGS_(m)′ are formed wider in the columndirection as compared with the first embodiment. With this arrangement,the non-volatile semiconductor storage device according to the secondembodiment can reduce a contact resistance between a first plugconductive layer 86 a and the source side selection gate line SGS_(m)′(source side conductive layer 421) and a contact resistance between thefirst plug conductive layer 86 a and the word lines WL_(m) 1′ to WL_(m)8′ (first to eighth word line conductive layers 321 a to 321 h) ascompared with the first embodiment.

Further, the non-volatile semiconductor device according to the secondembodiment does not form the memory separation grooves 94 between theU-shaped semiconductor layers 63 adjacent to each other in the columndirection in the manufacturing processes as compared with the firstembodiment. Accordingly, when the process (silicide process) shown inFIGS. 27 and 28 of the first embodiment is executed, since an aspectratio of a portion where a metal film is formed can be reduced, processstability can be improved in the silicide process.

Third Embodiment Arrangement of Non-Volatile Semiconductor StorageDevice According to Third Embodiment

Next, an arrangement of a non-volatile semiconductor storage deviceaccording to a third embodiment will be explained referring to FIGS. 49and 50. FIG. 49 is a schematic perspective view of a part of a memorytransistor region of the non-volatile semiconductor storage deviceaccording to the third embodiment, and FIG. 50 is a sectional view ofthe memory transistor region.

As shown in FIGS. 49 and 50, in the non-volatile semiconductor storagedevice according to the third embodiment, an arrangement of a back gateline BG′ (back gate transistor layer 20 a) is different from the firstembodiment. The back gate line BG′ (back gate transistor layer 20 a)according to the third embodiment has a first back gate line BG1′ (firstback gate conductive layer 22 a) and a second back gate line BG2′(second back gate conductive layer 22 b) formed on the first back gateline BG1′ (first back gate conductive layer 22 a). The first back gateline BG1′ (first back gate conductive layer 22 a) is formed such that itcovers the lower surface and the side surface of a coupling portionJP_(mn) (lower portion of a U-shaped semiconductor layer 63) as well asis formed up to the same height as the upper surface of the couplingportion JP_(mn) likewise the first embodiment. The second back gate lineBG2′ (second back gate conductive layer 22 b) is formed to cover theupper surface of the coupling portion JP_(mn) (coupling portion 63 a).

(Method of Manufacturing Non-Volatile Semiconductor Storage Deviceaccording to Third Embodiment)

Next, a method of manufacturing the non-volatile semiconductor storagedevice according to the third embodiment will be explained. In thenon-volatile semiconductor storage device according to the thirdembodiment, the first back gate conductive layer 22 a is formed throughthe processes shown in FIGS. 11 and 12 of the first embodiment.Subsequently, after first sacrificial layers 91 is formed, polysiliconis deposited on the first sacrificial layers 91, and the second backgate conductive layer 22 b is further formed. Thereafter, thenon-volatile semiconductor storage device according to the thirdembodiment shown in FIG. 50 is manufactured through the processes shownin FIGS. 13 to 46 of the first embodiment.

(Advantage of Non-Volatile Semiconductor Storage Device According toThird Embodiment)

The non-volatile semiconductor storage device according to the thirdembodiment achieves the same advantage as the first embodiment.

Further, the non-volatile semiconductor storage device according to thethird embodiment has the first back gate line BG1′, which covers thelower surface and the side surface of the coupling portion JP_(mn) aswell as is formed to the same height as the upper surface of thecoupling portion JP_(mn), and the second back gate line BG2′ whichcovers the upper end of the coupling portion JP_(mn). Accordingly, achannel can be formed around the entire periphery of the couplingportion JP_(mn) by the first back gate line BG1′ and the second backgate line BG2′. That is, the non-volatile semiconductor storage deviceaccording to the third embodiment can reduce the resistance of thecoupling portion JP_(mn) as compared with the first and secondembodiments.

Further, the design of the distance between the lowermost word lineWL_(mn) and the coupling portion JP_(mn) can be easily changed in themanufacturing process by changing only the thickness of the second backgate line BG2′ as compared with the first and second embodiments.

Fourth Embodiment Arrangement of Non-Volatile Semiconductor StorageDevice According to Forth Embodiment

Next, an arrangement of a non-volatile semiconductor storage deviceaccording to a fourth embodiment will be explained referring to FIG. 51.FIG. 51 is a schematic upper surface view of a part of a memorytransistor region of the non-volatile semiconductor storage deviceaccording to the fourth embodiment.

As shown in FIG. 51, in the non-volatile semiconductor storage deviceaccording to the fourth embodiment, word lines WL_(mn)″ are arrangeddifferent from the first embodiment.

In the fourth embodiment, respective word lines WL_(mn)″ have such ashape that they two-dimensionally expand in a row direction and a columndirection at respective positions in a lamination direction. Further,when viewed from upper surfaces, the respective word lines WL_(mn)″ arebroken (divided) so that they are made to a pair of comb shapes facingin the row direction about predetermined positions A in the rowdirection. More specifically, each of the word lines WL_(mn)″ iscomposed of a first word line WLa_(n)″ and a second word line WLb_(mn)″facing in the row direction.

The first word line WLa_(mn)″ and the second word line WLb_(mn)″ haveprojecting portions P extending in the row direction. The projectingportion P of the first word line WLa_(mn)″ is formed to surround one ofcolumnar portions CL_(mn) of a U-shaped semiconductor SC_(mn). Theprojecting portion P of the second word line WLb_(mn)″ is formed tosurround the other columnar portion CL_(mn) of the U-shapedsemiconductor SC_(mn).

A bit line BL is formed on the upper layers of a region B in which therespective word lines WL_(mn)″ are broken. More specifically, the regionB functions as a memory transistor region 12′.

(Advantage of Non-Volatile Semiconductor Storage Device According toForth Embodiment)

The non-volatile semiconductor storage device according to the fourthembodiment achieves the same advantage as the first embodiment.

Further, in the non-volatile semiconductor storage device according tothe fourth embodiment, the respective word lines WL_(mn)″ have such ashape that they two-dimensionally expand in the row direction and thecolumn direction at the respective positions in the lamination directionwhen viewed from the upper surfaces. Further, when viewed from the uppersurfaces, the respective word lines WL_(mn)″ are broken so that theymade to a comb shape about predetermined positions A in the rowdirection. Accordingly, in the non-volatile semiconductor storage deviceaccording to the fourth embodiment, since the word lines WL_(mn) are notprocessed to a line state as in the first to third embodiments, they canbe manufactured by manufacturing processes which are easier than thefirst to third embodiments. Further, a word line drive circuit 13 can bearranged as a common circuit by the arrangement of the word linesWL_(mn)″. Accordingly, in the non-volatile semiconductor storage deviceaccording to the fourth embodiment, an area occupied by a controlcircuit including the word line drive circuit 13 and the like can bereduced.

Other Embodiments

Although the embodiments of the non-volatile semiconductor storagedevice have been explained above, the present invention is not limitedto the embodiments, and various modifications, additions, replacements,and the like can be made within a scope which does not depart from thegist of the invention.

For example, in the first embodiment, the conductive voltage Vj isapplied to the back gate line BG when the read-out operation, the writeoperation, and then erase operation are executed, the conductive voltageVj may be applied thereto also in an ordinary operation.

Further, in the first embodiment, although the back gate conductivelayer 22 covers the lower surface and the side surface of the couplingportion 63 a of the U-shaped semiconductor layer 63, it may cover onlythe side surface of the coupling portion 63 a. Further, the back gateconductive layer 22 may cover only the bottom surface of the couplingportion 63 a.

The invention claimed is:
 1. A non-volatile semiconductor storage devicehaving: a first semiconductor layer extending in a first directionperpendicular to a surface of a substrate; a second semiconductor layerextending in a second direction perpendicular to the first direction,the second semiconductor layer being connected to a lower part of thefirst semiconductor layer; a first electrode layer disposed on a firstside surface of the first semiconductor layer; a first memory portiondisposed between the first semiconductor layer and the first electrodelayer; a second electrode layer disposed on a second side surface of thefirst semiconductor layer, the second electrode layer being disposedabove the first electrode layer; a second memory portion disposedbetween the first semiconductor layer and the second electrode layer;and a gate electrode layer extending in a plane parallel to the surfaceof the substrate, the gate electrode layer being disposed on an uppersurface of the second semiconductor layer.
 2. The non-volatilesemiconductor storage device according to claim 1, wherein the gateelectrode layer is disposed on a lower surface of the secondsemiconductor layer.
 3. The non-volatile semiconductor storage deviceaccording to claim 1, wherein the gate electrode layer is disposed on aside surface of the second semiconductor layer.
 4. The non-volatilesemiconductor storage device according to claim 1, further comprising: athird semiconductor layer extending in the first direction, the thirdsemiconductor layer being disposed at a position in a third directionperpendicular to the first and second directions from the firstsemiconductor layer; and a fourth semiconductor layer extending in thesecond direction, the fourth semiconductor layer being connected to alower part of the third semiconductor layer, wherein the gate electrodelayer is disposed on an upper surface of the fourth semiconductor layer.5. The non-volatile semiconductor storage device according to claim 1,wherein the gate electrode layer includes a first gate conductive layerand a second gate conductive layer disposed above the first gateconductive layer.
 6. The non-volatile semiconductor storage deviceaccording to claim 5, wherein a height of an upper surface of the firstgate conductive layer is the same as a height of the upper surface ofthe second semiconductor layer.
 7. The non-volatile semiconductorstorage device according to claim 6, wherein a height of a lower surfaceof the second gate conductive layer is the same as the height of theupper surface of the second semiconductor layer.
 8. The non-volatilesemiconductor storage device according to claim 1, further comprising: athird semiconductor layer extending in the first direction, the thirdsemiconductor layer being disposed at a position in a third directionperpendicular to the first and second directions from the firstsemiconductor layer; and a fourth semiconductor layer extending in thesecond direction, the fourth semiconductor layer being connected to alower part of the third semiconductor layer, wherein the first electrodelayer is disposed on a side surface of the third semiconductor, and thegate electrode layer is disposed between the first electrode layer andthe fourth semiconductor layer.
 9. A non-volatile semiconductor storagedevice having: a first semiconductor layer extending in a firstdirection perpendicular to a surface of a substrate; a secondsemiconductor layer extending in a second direction perpendicular to thefirst direction, the second semiconductor layer being connected to alower part of the first semiconductor layer; a first electrode layerdisposed on a first side surface of the first semiconductor layer; afirst memory portion disposed between the first semiconductor layer andthe first electrode layer; a second electrode layer disposed on a secondside surface of the first semiconductor layer, the second electrodelayer being disposed above the first electrode layer; a second memoryportion disposed between the first semiconductor layer and the secondelectrode layer; and a gate electrode layer extending in a planeparallel to the surface of the substrate, the gate electrode layer beingdisposed between the first electrode layer and the second semiconductorlayer.
 10. The non-volatile semiconductor storage device according toclaim 9, wherein the gate electrode layer is disposed on a lower surfaceof the second semiconductor layer.
 11. The non-volatile semiconductorstorage device according to claim 9, wherein the gate electrode layer isdisposed on a side surface of the second semiconductor layer.
 12. Thenon-volatile semiconductor storage device according to claim 9, whereinthe gate electrode layer includes a first gate conductive layer and asecond gate conductive layer disposed above the first gate conductivelayer.
 13. The non-volatile semiconductor storage device according toclaim 12, wherein a height of an upper surface of the first gateconductive layer is the same as a height of the upper surface of thesecond semiconductor layer.
 14. The non-volatile semiconductor storagedevice according to claim 13, wherein a height of a lower surface of thesecond gate conductive layer is the same as the height of the uppersurface of the second semiconductor layer.
 15. A non-volatilesemiconductor storage device having: a first semiconductor layerextending in a first direction perpendicular to a surface of asubstrate; a second semiconductor layer extending in a second directionperpendicular to the first direction, the second semiconductor layerbeing connected to a lower part of the first semiconductor layer; afirst electrode layer disposed on a first side surface of the firstsemiconductor layer; a first memory portion disposed between the firstsemiconductor layer and the first electrode layer; a second electrodelayer disposed on a second side surface of the first semiconductorlayer, the second electrode layer being disposed above the firstelectrode layer; a second memory portion disposed between the firstsemiconductor layer and the second electrode layer; and a gate electrodelayer surrounding a third side surface of the first semiconductor layer,the gate electrode layer being disposed on an upper surface of thesecond semiconductor layer and between the first electrode layer and thesecond semiconductor layer.
 16. The non-volatile semiconductor storagedevice according to claim 15, wherein the gate electrode layer isdisposed on a lower surface of the second semiconductor layer.
 17. Thenon-volatile semiconductor storage device according to claim 15, whereinthe gate electrode layer is disposed on a side surface of the secondsemiconductor layer.
 18. The non-volatile semiconductor storage deviceaccording to claim 15, further comprising: a third semiconductor layerextending in the first direction, the third semiconductor layer beingdisposed at a position in a third direction perpendicular to the firstand second directions from the first semiconductor layer; and a fourthsemiconductor layer extending in the second direction, the fourthsemiconductor layer being connected to a lower part of the thirdsemiconductor layer, wherein the first electrode layer is disposed on afirst side surface of the third semiconductor layer, and the gateelectrode layer surrounds a second side surface of the thirdsemiconductor layer, the gate electrode layer being disposed on an uppersurface of the fourth semiconductor layer and between the firstelectrode layer and the fourth semiconductor layer.
 19. The non-volatilesemiconductor storage device according to claim 15, wherein the gateelectrode layer includes a first gate conductive layer and a second gateconductive layer disposed above the first gate conductive layer.
 20. Thenon-volatile semiconductor storage device according to claim 19, whereina height of an upper surface of the first gate conductive layer is thesame as a height of the upper surface of the second semiconductor layer.